Best way to swap a hard drive in MBP

So I'm finally replacing my PowerBook with a new base model 13" MBP. I've ordered a 640gb Samsung Spinpoint hd to replace the 250 gb stock hd. I've also purchased a Rosewill external to put the stock hd into (all this for less than Apple would have charged to upgrade to a 500gb hd!).

Here's the issue: what's the best way to swap hard drives?

1) Put the new one in, and use the recovery discs to install the OS; or

2) Put the new one in the enclosure, clone the hard drive in the mpb, then swap them; or

Oh man. The PowerBook has been on its last leg for awhile, so whatever is on it is also on my iMac. Seriously, I'm amazed this thing is still alive. The battery completely puked about six months ago. I think the power management system is dead or needs a battery or something, because whenever the computer goes to sleep, I need to press shift-control-option-power and wait five seconds to press the power button again before it'll boot.

I'm having a hard time letting this beast go, but I need a laptop that I can actually use like a laptop. Sigh.

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